“At a time when the Department of Health’s budget is under severe pressure there are serious questions about how the increased use of private ambulances provides value for money in the long term”, he said.

“I will be seeking answers from the Health Minister about the awarding of these contracts and whether this represents a departmental policy of increasing privatisation of our Health Service.”

UK ambulance trusts said they had little choice, warning of a “national shortage of paramedics”.

The figures were revealed last week by the Department of Health at the Northern Ireland Assembly.

The Western Board had the biggest increase in private ambulance use rising more than twentyfold from £12,000 in 2009/10 to £215,000 in 2014, while the use almost quadrupled in the Southern Trust area.